I saw this episode for the first time since I was a kid. I was really surprised how good it was. For years it had been the reason that I hated the show in the later seasons, because the episode seemed like the height of sitcom stupidity. But today I realized that it was supposed to be a dream.

It had a really unique and realistic dreamlike quality. The demon nephew even had the power to move around from place to place supernaturally, to appear and disappear, not that the special effects were that great.

This episode was also used as a vehicle for another spinoff sitcom. I think the show was called "Out of the Blue." It didn't last very long. It centered around the angel who helped Fonzie overcome his temptations from the dancing women at Arnold's. But I think the new show was set in modern day times, just like Mork and Mindy.

Out of the Blue wasn't a spinoff. That was a crossover episode. OotB premiered September 9th and Random, the angel, didn't appear on Happy Days until Septermber 18th.

That's possible. I don't really remember much about either show back then. But I'm sure the appearance on HD was as much publicity as any new show could have wanted at the time.